A string used in a string musical instrument such as a piano is, as shown in FIG. 8, fastened at one end thereof to a hitch pin (not shown) provided on a frame 7 while the other end thereof is wound onto a tuning pin 1 partly screwed into a pin board 8. This tuning pin 1 holds a string 9 set in place and is finely tuned to increase or decrease tension of the string 9 for adjustment of the musical sound pitch of the string. Reference numeral 10 denotes a string depresser.
To accomplish the above purposes, the conventional system has, as shown in FIG. 9, a tuning pin 1 made of a carbon steel cylinder measuring about 7 mm in diameter and 60 mm in length. The tuning pin 1 is machined to form thereon a threaded portion 2 measuring about 35 mm long while a head portion 3 of the tuning pin 1 is formed to have a rectangular section for cooperating with a tuning hammer, which is a tool used to turn the pin. The head portion is provided with a string hole 4 into which the string 9 can be inserted.
The tuning pin 1D of this type in which the threads are cut by machining has, as shown in FIG. 10, a number of scale-shaped machining specks 11 on the surface of the threaded portion 1, each speck being several microns in size. These machining specks 11 serve to provide adequate friction between the tuning pin 1 and the pin board 8, thus enabling a delicate fine tuning of the string to be obtained. However, tuning pin 1D having such specks is manufactured through complicated steps which inevitably result in a higher cost.
On the other hand, threaded portion 2 of a tuning pin 1E can be formed by a roll threading process, as proposed by others and as shown in FIG. 11. Such a tuning pin 1E can be manufactured at low cost. However, compared with tuning pin 1D, which has the threaded portion 2 formed by machining, the threaded portion of tuning pin 1E has a smoother surface, so that when the tuning pin 1E is turned for tuning of the string, slipping between the pin board 8 and the tuning pin 1E causes the pin to race, thus making it difficult to carry out fine adjustment during a tuning operation.